Reinforcement system at railway tunnel section passing through karst cave with large dip angle and construction method

Abstract

The present invention relates to a reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle and a construction method. The reinforcement system of the present invention can solve the problems of downward mud filling, watertightness, etc. of a top through structures of an umbrella arch, a concrete layer, a flexible buffer layer and a protective layer at the top, at a karst cave, of a tunnel, solve the problem of upward mud inrush at a bottom through structures of an anchor cable, a ring beam and a foundation pad at the bottom of the tunnel, guarantee stability of an arch bridge by erecting “a triple arch bridge” in a middle and adding a vertical bearing wall under the arch bridge, and make a railway safely cross the mud-inrush karst cave by safely laying a ballastless track on the bridge.

What is claimed is: 
     
       1. A reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle, specifically comprising:
 an umbrella arch ( 1 - 1 ), a concrete layer ( 1 - 2 ), a flexible buffer layer ( 1 - 3 ) and a protective layer ( 1 - 4 ) which are sequentially built at a top of a portion, of a main tunnel ( 1 ) from bottom to top, passing through the karst cave; and 
 an arch bridge ( 4 ) which is built at a bottom of a portion, of the main tunnel ( 1 ), passing through the karst cave, wherein a filling layer ( 4 - 1 ) is arranged over the arch bridge ( 4 ), two arched door openings ( 4 - 2 ) are reserved at portions, on two sides of the arch bridge ( 4 ), of the filling layer ( 4 - 1 ), a bottom plate ( 4 - 3 ) is arranged over the filling layer ( 4 - 1 ), a foundation pad ( 3 - 1 ) is arranged at a bottom of a foundation pit ( 3 ) under the arch bridge ( 4 ), and a vertical bearing wall ( 4 - 4 ) is built between the arch bridge ( 4 ) and the foundation pad ( 3 - 1 ). 
 
     
     
       2. The reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle according to  claim 1 , further comprising an emptying culvert ( 2 ) parallel to the main tunnel ( 1 ), a bottom surface of the emptying culvert ( 2 ) being lower than the bottom plate ( 4 - 3 ) in height. 
     
     
       3. The reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle according to  claim 2 , wherein
 a cross passage ( 2 - 1 ) is built between the main tunnel ( 1 ) and the emptying culvert ( 2 ); 
 a construction cross passage ( 2 - 2 ) is built between the emptying culvert ( 2 ) and a lower portion of the arch bridge ( 4 ), openings of the construction cross passage ( 2 - 2 ) being located on two sides of the vertical bearing wall ( 4 - 4 ); and 
 a circuitous passage ( 2 - 3 ) is built between the cross passage ( 2 - 1 ) and an upper portion of the protective layer ( 1 - 4 ). 
 
     
     
       4. The reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle according to  claim 3 , wherein the protective layer ( 1 - 4 ) is in a shape of a cone with a lower portion wider than an upper portion, and a cone top inclining to a side far away from the circuitous passage ( 2 - 3 ). 
     
     
       5. The reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle according to  claim 1 , wherein the foundation pad ( 3 - 1 ) comprises a ring beam ( 3 - 11 ), an intermediate beam ( 3 - 12 ) and a pad layer ( 3 - 13 ), several anchor cables ( 3 - 14 ) penetrating into a wall of the karst cave are arranged at half of a height of the foundation pad ( 3 - 1 ), and the vertical bearing wall ( 4 - 4 ) is arranged on the intermediate beam ( 3 - 12 ). 
     
     
       6. A construction method of a reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle, specifically comprising:
 (I) building a protection at a tunnel top 
 building an umbrella arch ( 1 - 1 ) at a top of a portion, of a main tunnel ( 1 ), passing through a karst cave, filling a top of the umbrella arch ( 1 - 1 ) with plain concrete to form a concrete layer ( 1 - 2 ), stacking a sandbag on the concrete layer ( 1 - 2 ) to serve as a flexible buffer layer ( 1 - 3 ), and pouring reinforced concrete at a top of the flexible buffer layer ( 1 - 3 ) to form a protective layer ( 1 - 4 ); 
 (II) building a foundation pit 
 excavating the foundation pit ( 3 ) at a bottom of a portion, of the main tunnel ( 1 ), passing through the karst cave; 
 driving, after excavation, anchor cables ( 3 - 14 ) into walls of the karst cave on a periphery of a bottom of the foundation pit ( 3 ) for fixing, wherein a free end of one anchor cable ( 3 - 14 ) and a free end of another anchor cable ( 3 - 14 ) driven into opposite walls of the karst cave are fastened together by a buckle ( 3 - 15 ); and 
 erecting reinforced beams on the periphery and in a middle of the bottom of the foundation pit ( 3 ), wherein the anchor cables ( 3 - 14 ) are located at halves of heights of the erected reinforced beams, pouring concrete to form a ring beam ( 3 - 11 ) and an intermediate beam ( 3 - 12 ), pouring concrete in a space between the ring beam ( 3 - 11 ) and the intermediate beam ( 3 - 12 ) to form a pad layer ( 3 - 13 ), and building a foundation pad ( 3 - 1 ); and 
 (III) building an arch bridge 
 erecting, after step (II), an arch bridge ( 4 ) by using reinforced concrete, pouring plain concrete at a top of the arch bridge ( 4 ) to form a filling layer ( 4 - 1 ), and pouring reinforced concrete on an upper portion of the filling layer ( 4 - 1 ) to serve as a bottom plate ( 4 - 3 ). 
 
     
     
       7. The construction method of the reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle according to  claim 6 , further comprising:
 before step (I), building an emptying culvert ( 2 ) beside the main tunnel ( 1 ) firstly, wherein the emptying culvert ( 2 ) is parallel to the main tunnel ( 1 ), and a bottom surface of the emptying culvert ( 2 ) is lower than the bottom plate ( 4 - 3 ) in height; 
 building a cross passage ( 2 - 1 ) between the main tunnel ( 1 ) and the emptying culvert ( 2 ), wherein an included angle of 45° is formed between the cross passage ( 2 - 1 ) and the main tunnel ( 1 ); 
 building a construction cross passage ( 2 - 2 ) between the emptying culvert ( 2 ) and a space below the arch bridge ( 4 ) and above the foundation pad ( 3 - 1 ); and 
 building a circuitous passage ( 2 - 3 ) between the cross passage ( 2 - 1 ) and an upper portion of the protective layer ( 1 - 4 ), a bottom edge of an opening, at the upper portion of the protective layer ( 1 - 4 ), of the circuitous passage ( 2 - 3 ) coincides with a bottom edge of the protective layer ( 1 - 4 ) or is slightly lower than the bottom edge of the protective layer ( 1 - 4 ). 
 
     
     
       8. The construction method of the reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle according to  claim 7 , further comprising: after step (III), building a vertical bearing wall ( 4 - 4 ) between the arch bridge ( 4 ) and the foundation pad ( 3 - 1 ), and a bottom of the vertical bearing wall ( 4 - 4 ) is arranged on the intermediate beam ( 3 - 12 ). 
     
     
       9. The construction method of the reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle according to  claim 8 , further comprising:
 building a passage door is built on the vertical bearing wall ( 4 - 4 ), and openings of the construction cross passage ( 2 - 2 ) are located on two sides of the vertical bearing wall ( 4 - 4 ). 
 
     
     
       10. The construction method of the reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle according to  claim 7 , wherein the protective layer ( 1 - 4 ) is in a shape of a cone with a lower portion wider than an upper portion, and a cone top inclining to a side far away from the circuitous passage ( 2 - 3 ).